Understand the movement of planetary bodies. Complex Knowledge: demonstrations of learning that go aboveand above and beyond what was explicitly taught. Knowledge: meeting the learning goals and expectations. Foundational knowledge: simpler procedures, isolated details, vocabulary. Limited knowledge: know very little details but working toward a higher level. Understand how our view of the solar system has changed over time and how discoveries made have led to our changing our view of the solar system. Learn planetary characteristics such as number of moons, size, composition, type of atmosphere, gravity, temperature and surface features. Understand the movement of planetary bodies. Understand which planetary characteristics are more important than others when it relates to our understanding of other worlds. Understand how proximity to the sun influences planets. Understand the methods and tools scientists use to learn about other planets and moons in our solar system. Understand the conditions needed for a habitable world and determine if there are habitable worlds in our solar system or outside the solar system. Understand how we look for and study solar systems other than our own.

Formation of the Solar System

This Week’s questions: Are all planets created equal? What events and materials were necessary to form our solar system? How do planets differ from one another and why?

Any model of Solar System formation must explain the following facts: All the orbits of the planets are prograde (i.e. if seen from above the North pole of the Sun they all revolve in a counter-clockwise direction). All the planets have orbital planes that are inclined by less than 6 degrees with respect to each other (i.e. all in the same plane- ecliptic). Terrestrial planets are dense, rocky and small, while Jovian planets are gaseous and large.

Lets get more specific Any model must explain that Planets are relatively isolated in space Planetary orbits are nearly circular Planetary orbits all lie in (nearly) the same plane Direction of orbital motion is the same as direction of Sun’s rotation Direction of most planets’ rotation is also the same as the Sun’s

Modeling Planet Formation (cont.) 6. Most moons’ orbits are also in the same direction 7. Solar system is highly differentiated 8. Asteroids are very old, and not like either inner or outer planets 9. Kuiper belt, asteroid-sized icy bodies beyond the orbit of Neptune 10. Oort cloud is similar to Kuiper belt in composition, but farther out and with random orbits

Statistics of our Solar System Sun contains 99.8% of the total mass of the solar system 74% hydrogen 24% helium 2% all other elements Metals - 0.2% Rocks - 0.4% Ices – 1.4% Light gases - 98%

Modeling Planet Formation Solar system is evidently not a random assemblage, but has a single origin. Planetary condensation theory, or Nebular Theory seems to work well. Lots of room for variation; there are also irregularities (Uranus’s axial tilt, Venus’s retrograde rotation, etc.) that must be allowed for by the model.

Nebular Theory/Solar Nebular Disk Model Nebular theory is the most widely accepted model explaining the formation of the Solar System. First proposed with evidence by: Emanuel Swedenborg, Immanuel Kant, and  Pierre-Simon Laplace in 1734 Originally applied only to our own Solar System, this method of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is Solar Nebular Disk Model (SNDM) or simply Solar Nebular Model.

Steps to a Solar System….in..1, 2, 3ish steps

Step 1 –formation of a star stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds (GMC). matter coalesces through gravity to create smaller denser clumps Continue to collapse to form proto-stars that will eventually end up as Brand new stars!  sun-like stars usually take about 50 million years to form

Step 1 –formation of a star star formation produces a gaseous proto-planetary disk around the young stars Why? As the gas cloud collapses it starts to spin and flatten out Think Figure Skaters and Pizzas formation of planetary systems is thought to be a natural result of star formation

Why did the gas cloud suddenly collapse? We have no clue May have been a passing star near the gas cloud We think it was a nearby supernova shockwave that smooshed up the gas against itself

Pinwheel Galaxy –21 mly from Earth

Step 1 –formation of a star stars form in massive and dense clouds of molecular hydrogen—giant molecular clouds (GMC). gravitationally unstable matter coalesces to smaller denser clumps Collapses to form proto-stars that will eventually end up as Brand new stars!  star formation produces a gaseous proto-planetary disk around the young stars formation of planetary systems is thought to be a natural result of star formation sun-like stars usually take about 50 million years to form

Step 2 – form terrestrial planets Proto-planetary disks are accretion disks which continue to feed the central star. But, If the disk is massive enough, accretions begin in outer areas as well small dust grains and rocks are plentiful and coagulate into kilometers-wide sized planetesimals rapid—100,000 to 300,000 years—formation of Moon- to Mars-sized planetary embryos. the planetesimals go through violent mergers, producing a few terrestrial planets. Planets take around 100 million to a billion years to form

Planetesimal Planetesimal Collisions

Pause Please head to Google Classroom and work on the activity posted there. You need to answer 7 questions, so you have 7 minutes. Well, now less than 7 minutes….. The worksheet is posted on the assignment as a pdf Your answer sheet is a google doc with your name already on it (you have to OPEN THE ASSIGNMENT to see it)

Step 2 – form terrestrial planets Proto-planetary disks are accretion disks which continue to feed the central star. But, If the disk is massive enough, accretions begin in outer areas as well small dust grains and rocks are plentiful and coagulate into kilometers-wide sized planetesimals rapid—100,000 to 300,000 years—formation of Moon- to Mars-sized planetary embryos. the planetesimals go through violent mergers, producing a few terrestrial planets. Planets take around 100 million to a billion years to form -- Gases don’t condense into ice but instead get blown outward by the solar wind

Step 3 –form the gas giants beyond the “snow line” planetary embryos begin to form and are mainly made of various ices. Now you can also use things like frozen methane, water and ammonia Also several times more massive than the inner part of the disk Ices stick together better than rocks, so they grew in size more efficiently formation of giant planets is a more complicated process some embryos appear to continue to grow and eventually reach 5–10 Earth masses—the threshold value, which is necessary to begin accretion of the hydrogen–helium gas from the disk. accumulation of gas by the core is initially a slow process, which continues for several million years after the forming proto-planet reaches about 30 Earth masses it accelerates and proceeds in a runaway manner.

3 –gas giants Jupiter and Saturn–like planets are thought to accumulate the bulk of their mass during only 10,000 years. The accretion stops when the gas is exhausted. Because their gravity is so strong, the newly formed planets can migrate over long distances during or after their formation. The ice giants like Uranus and Neptune are thought to be failed cores, which formed too late when the disk had almost disappeared.

The Nebular Theory

This accounts for the other solar system stuff too… Moons Comets/icy planetesimals Asteroids Dwarf planets Kuiper belt & Oort cloud objects Rings